1. Field of the Invention
The present invention relates to a method and device for mechanically imaging the prostate. It is also applicable to mechanical imaging of tissues and glands, including but not limited to, through natural openings in a human being, i.e. mouth, ear(s), rectum, etc. channels. It is also applicable to determination of relative stiffness or elasticity of tissues or glands, i.e. breast. In all cases both human beings and animals, both alive and dead, can be a subject for mechanically imaging.
2. Description of Related Art
Conventional methods for early detection of prostate cancer include digital rectal examination (DRE). Digital rectal examination or palpation, that is an examination using the sense of touch, is based on the significant differences in elasticity of normal tissues and certain lesions. Palpation has been a commonly used test by general practitioners and specialists and is recommended as a part of an annual general preventive physical examination for all men 40 years of age and older. The effectiveness and reliability of palpation is dependent on the level of skill of the examiner, since the finger as an instrument does not provide any quantitative information, and therefore the examiner must instinctively relate what he/she senses by the finger to their previous experience with palpation, as described in Littrup et al., The Benefit and Cost of Prostate Cancer Early Detection, CA Cancer Journ. for Clinicians, Vol. 43, pp. 134-149 (1993). It has been found that the disagreement between the palpatory findings of experienced urologists is about 20%, as described in Smith et al., Interexaminer Variability of Digital Rectal Examination in Detecting Prostate Cancer, Urology, Vol. 45, pp. 70-74 (1995). The disagreement within inexperienced examiners, who are most likely to carry the bulk of cancer screening, is much higher. Once a lesion is palpated, documentation of the abnormality depends on the precision of a physician""s description or a freehand diagram.
Several authors have proposed various types of devices mimicking palpation to detect tumors using different types of pressure sensors. For example, U.S. Pat. No. 4,250,894, describes an instrument for breast examination that uses a plurality of spaced piezoelectric strips which are pressed into the body being examined by a pressure member which applies a given periodic or steady stress to the tissue beneath the strips.
Another approach to evaluate the elasticity of the tissues uses indirect means, such as conventional imaging modalities (ultrasound or MRI) which are capable of detecting motion of a tissue subjected to an external force. One approach attempts to determine the relative stiffness or elasticity of tissue by applying ultrasound-imaging techniques while vibrating the tissue at low frequencies. See, e.g., J. J. Parker et al., U.S. Pat. No. 5,099,848; R. M. Learner et al., Sono-Elasticity: Medical Elasticity Images Derived From Ultrasound Signals in Mechanically Vibrated Targets, Acoustical Imaging, Vol. 16, 317 (1988); T. A. Krouskop et al., A Pulsed Doppler Ultrasonic System for Making Non-Invasive Measurement of Mechanical Properties of Soft Tissue, 24 J. Rehab. Res. Dev. Vol. 24, 1 (1987); Y. Yamakoshi et al., Ultrasonic Imaging of Internal Vibration of Soft Tissue Under Forced Vibration, IEEE Transactions on Ultrasonics Ferroelectrics, and Frequency Control, Vol. 7, No. 2, Page 45 (1990).
U.S. Pat. Nos. 6,142,959; 5,922,018 and 5,836,894 to Sarvazyan et al., describe devices for mechanical imaging of the prostate using a transrectal probe. The prostate imaging is achieved by evaluating the spatial changes of stress pattern over the prostate compressed by the probe. The devices enable physicians to quantitatively and objectively characterize geometrical and mechanical features of the prostate. However, the physician doesn""t have a feedback in real time, while prostate examination, which decreases the data collection efficacy.
It is desirable to provide an improved real time method and device for palpation and mechanical imaging of the prostate.
The present invention relates to a method for real time mechanically imaging the prostate with a transrectal probe. The present invention provides a means for electronic palpation of the prostate, objective and quantitative assessment of the prostate conditions using tactile sensors. In the method, the prostate image is synthesized and displayed in real time during the examination process. In a preferred embodiment, the compact prostate examination device comprises a probe sized to fit within the rectum and having a head with a tactile sensor longer than the axial length of an average prostate, an electronic unit and a display. As the pressure sensing part of the head is pressed against and moved over the prostate, it generates signals characterizing mechanical structure of the examined area. An accelerometer-based motion tracking system is mounted in the probe for determining the position of the pressure transducer array during prostate examination. The electronic unit incorporated into the handle of the probe receives the pressure and motion data to calculate mechanical and geometrical features of the prostate and displays it on the display.
Preferably, the tactile sensor includes a plurality of accelerometers to be used as a motion tracking system for determination of probe coordinates relative to the examined prostate. In an alternate preferred embodiment of the present invention the tactile sensor comprises a magnetometer-based motion tracking system. Thereafter, the pressure response is used in real time to generate mechanical imaging results. Alternatively, the method and device can be used for real time mechanically imaging any gland or tissue.
The invention will be more fully described by reference to the following drawings.